When a medical intervention is being carried out on an object under examination, perhaps a human or animal body, the status of the object under examination is generally controlled in a manner that is appropriate for the intervention risk. Body functions of the object under examination are recorded for this purpose. In the case ofan intervention with a medical device inserted at least partially into the object under examination, the position and/or optionally the location of the medical instrument within the object under examination is of interest as well as patient status.
Examples of medical instruments are catheters, guide wires, stents, sheaths, biopsy needles or other means that are inserted at least partially into the object under examination during medical interventions.
In order to be able to determine the site and/or spatial orientation of the medical instrument, a method is required, which allows the locating—in other words determination of the position and/or location—of the medical instrument. Medical personnel also have to determine any changes in the position and/or location of the medical instrument on a continuous basis, in order to control the insertion into or further progress of the medical instrument in the object under examination. Such a method can increase the accuracy of the intervention, reduce damage to the object under examination and improve patient safety.
A method for determining the position of a medical instrument is known from the published patent application DE 100 04 764 A1. The first method step comprises the pre-operative acquisition of computed tomograms, which make it possible to generate a three-dimensional image data record before the actual medical intervention on the object under examination. This is followed by an intra-operative method step, wherein two-dimensional images are acquired using an x-ray device during the intervention on the object under examination and used to determine the position of the medical instrument.
A position measuring device is also provided for the extra-corporal determination of the position of the medical instrument. The position of the medical instrument within the three-dimensional image data record is also calculated by data assignment of the image data generated pre-operatively and intra-operatively. Disadvantages of this method result for example from the cost of additional pre-operative x-ray examinations and the existing installation of a position measuring device.
This results on the one hand in additional examination outlay, in other words in the case of a computed tomography method additional radiation exposure for the patient. Also the position determination can easily be adversely affected if medical personnel cover the reference points for the position determination, which are for example attached in the form of infrared lights. Also the time difference between pre-operative data acquisition and intra-operative data acquisition can result in an inaccurate position determination due to a corresponding change in the state of the patient during this time period.